The US is planning a number of other hypersonic planes

The initial description of the concept - called the Hypersonic Cruise Vehicle (HCV) - has recently been placed on the website of the Defense Advanced Research Projects Agency (Darpa), the central research and development organisation of the Pentagon.

A conference of companies interested in the project is to be held soon.

The idea is that the HCV would take off from a conventional airfield in the continental United States carrying a 12,000-pound (5,500-kilogram) payload.

The HCV air/spacecraft could be operational by 2025.

Advanced capability

Darpa says: "This capability would free the US military from reliance on forward basing to enable it to react promptly and decisively to destabilising or threatening actions by hostile countries and terrorist organisations."

The US will be able, using aircraft based on its own territory, to strike at individual targets without warning and without the need for foreign bases

It appears that the philosophy is a development of the "shock and awe" tactics developed for the Iraq war.

According to Darpa: "The intent is to hold adversary vital interests at risk at all times, counter anti-access threats, serve as a halt-phase shock force and conduct suppression of enemy air-defence and lethal strike missions as part of integrated strategic campaigns in the 21st Century."

In other words the United States will be able, using aircraft based on its own territory, to strike at individual targets without warning and without the need for foreign bases.

The whole project goes under the acronym Falcon - Force Application and Launch from the Continental United States.

The military journal Jane's Defence Weekly, which broke the story in its latest edition, says that as well as this futuristic plan, the research agency also proposes a shorter term (by 2010) weapons system.

It would be based on what is known as a Small Launch Vehicle (SLV) which would blast into space carrying the Common Aero Vehicle.

This is essentially a bomb dropped from space which then freefalls or glides on to its target.

The current and future international political environment severely constrains this country's ability to conduct long-range strike missions Darpa

It is officially described as "an unpowered, manoeuvrable, hypersonic glide vehicle capable of carrying approximately 1,000 pounds (453 kg) of munitions". Its range would be about 3,000 miles (4,800 kilometres) and it would be accurate to within 3 metres.

It would be going so fast that its small warhead would not matter much since it would hit the target with such force.

There are plans also to make the SLV capable of launching small satellites into orbit at very short notice in order to respond to a specific crisis.

New technology sought

The new systems are being developed in response to what are seen as the inadequacies of current technology, which, though smart, are not smart enough.

Darpa says: "Recent military engagements in Bosnia, Afghanistan and Iraq have underscored both the capabilities and limitations of US air forces in terms of placing ordnance on military targets.

"Moreover, the current and future international political environment severely constrains this country's ability to conduct long-range strike missions on high-value time-critical targets from outside CONUS [the continental United States]."

The plan is that the first Cav flight should take place in 2006 and the SLV in 2007 with the first test flight of both together in 2009.